The present invention relates generally to an air break disconnect switch for high voltage electrical applications and, more particularly, to an in-line high voltage air break disconnect switch that mounts in-line with the transmission or substation line conductor without the need of a group operated switch with associated ground supported mounting structure. Such an in-line high voltage disconnect switch hangs from and is supported by its associated power line.
One example of such an in-line high voltage disconnect switch is a disconnect switch currently manufactured and sold by Cleaveland/Price Inc., of Trafford, Pa., the present Assignee, as a type ILO-C, Hookstick Operated In-Line Transmission Switch. The switch is described in Cleaveland/Price Bulletin DB-1021B11, entitled “Type ILO-C Hookstick Operated In-Line Transmission Switch 69 kV-230 kV 1200 A.”. The switch is rated 69 kV-230 kV, 1200 amperes. The Cleaveland/Price Inc. type ILO-C In-Line high voltage disconnect switch utilizes a manually operated hookstick for engaging an operating eye ring attached to the breakjaw end of the switch blade of the switch. The hookstick when engaged with the operating ring imparts rotation about the hinge end of the switch blade for opening and closing of the switch. The Cleaveland/Price Inc. type ILO-C In-Line high voltage disconnect switch is a single phase switch and is versatile and can serve many functions on a three phase system. The switch can be used to sectionalize long transmission lines, disconnect lines from substations, serve as a line tap switch, and serve as a temporary maintenance switch, for example. The Cleaveland/Price Inc. type ILO-C In-Line high voltage disconnect switch saves significant installation costs compared to a non-in-line switch installed via direct ground support mounting structure. The Cleaveland/Price Inc. type ILO-C high voltage disconnect switch allows for easy, cost efficient sectionalizing of high voltage transmission lines and isolation in high voltage substations. As a result of this, the type ILO-C In-Line high voltage disconnect switch has been used by electric utilities for many years to isolate transmission and substation circuits.
In recent years the electric utility industry has been interested in modernizing the electrical power infrastructure. It is also of concern that the electric system in the U.S.A. is vulnerable to attack by “terrorists”. Nearly every electric switch in a substation or on a transmission line is mechanically operated at ground level by a swing handle, geared hand crank or motor operator which is only secured from operation by a padlock which can be easily cut with bolt cutters. The cutting of the padlock gives the “terrorist” the ability to operate the switch which may damage the switch and may cause power outages. It is therefore an object of this invention to provide an improved in-line high voltage disconnect switch that may be used in applications for switching the electric power grid while preventing “terrorists” from being able operate the switch.